[petsc-users] log_summary time ratio and flops ratio

[Xiangdong]

If I want to know whether only rank 0 is slow (since it may has more io) or
actually a portion of cores are slow, what tools can I start with?

Thanks.

Xiangdong

On Fri, Feb 5, 2016 at 5:27 PM, Jed Brown <jed at jedbrown.org> wrote:

> Matthew Knepley <knepley at gmail.com> writes:
> >> I attached the full summary. At the end, it has
> >>
> >> Average time to get PetscTime(): 0
> >> Average time for MPI_Barrier(): 8.3971e-05
> >> Average time for zero size MPI_Send(): 7.16746e-06
> >>
> >> Is it an indication of slow network?
> >>
> >
> > I think so. It takes nearly 100 microseconds to synchronize processes.
>
> Edison with 65536 processes:
> Average time for MPI_Barrier(): 4.23908e-05
> Average time for zero size MPI_Send(): 2.46466e-06
>
> Mira with 16384 processes:
> Average time for MPI_Barrier(): 5.7075e-06
> Average time for zero size MPI_Send(): 1.33179e-05
>
> Titan with 131072 processes:
> Average time for MPI_Barrier(): 0.000368595
> Average time for zero size MPI_Send(): 1.71567e-05
>
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